JPS6165672A - Automatic focusing device for video camera - Google Patents

Abstract

PURPOSE:To execute a response of a gain control circuit quickly and to remove a modulating signal by installing a clip circuit to clip a modulating signal. CONSTITUTION:A changing object is modulated for an optical path with a focus lens 1 and light modulated for the optical path with an image pick-up device 2 is set to an video signal and set to the video signal of a constant level by a gain control circuit 3. The output is detected by a detecting circuit 4 and becomes a modulating signal, but, the modulating signal is clipped and only a video signal, which will not include the modulating signal, becomes a control signal of the gain control circuit 3 through a peak holding circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an autofocus device for a video camera.

Conventional configuration and its problems Traditionally, in this type of equipment, a modulation signal is extracted from the output of the imaging device, and in those that perform automatic focus adjustment, the output of the imaging device is added to a gain control circuit and detected from the gain control circuit. and extracts the modulated signal.

If you integrate the gain control signal, the response will be slow.

Therefore, if the response is made faster, the modulation signal enters the gain control circuit system, and there is a drawback that the modulation signal is no longer output.

OBJECTS OF THE INVENTION The present invention overcomes the drawbacks of the above-mentioned conventional example, and aims to speed up the response of a gain control circuit and extract a modulated signal.

Structure of the Invention In order to achieve the above object, the present invention includes a clip circuit that clips the modulation signal in order to prevent the modulation signal from being added to the gain control signal.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings.

1 is a focus lens that modulates the optical path of the subject.

2 is an imaging device that converts the modulated light into a video signal;
3 is a gain control circuit, 4 is a detection circuit that converts the signal into DC, 5 is a clip circuit that clips only the modulation signal, 6 is a peak hold circuit that holds the peak of the DC signal and uses it as a gain control signal, and 7 is the modulation signal This is the output terminal of The operation in the above configuration will be explained.

Modulate the optical path of the changing subject with focus lens 1,
The light path-modulated by the imaging device 2 is converted into a video signal, and the gain-in control circuit 3 converts the light into a video signal at a constant level. This output is detected by the detection circuit 4 and becomes a modulated signal, but this modulated signal is clipped by the clip circuit 5.
Only the video signal containing no modulation signal passes through the peak hold circuit 6 and becomes a control signal for the cane control circuit 3.

Effects of the Invention As is clear from the above explanation, according to the present invention, since the modulation signal is clipped, the response of the gain control circuit can be made faster, and the focus ring for automatic focusing can be adjusted using the modulation signal information. It can be rotated quickly and the focusing speed can be increased, which is advantageous in practice.

[Brief explanation of the drawing]

The drawing is a block diagram of an automatic focusing device for a video camera in one embodiment of the present invention. 1... Focus lens, 2... Imaging device, 3
...Gain control circuit, 4...Detection circuit, 5
...Clip circuit, 6...Beekholt circuit, 7.
...Output terminal.

Claims (1)

[Claims] An automatic focusing device for a video camera, in which an output circuit of an imaging device that outputs a video signal including a modulated signal is provided with a gain control circuit, a clip circuit that clips the modulated signal, and a circuit that uses the output of the clip circuit as a gain control signal. .